1. Field of the Invention
The invention relates to an alarm system and, in particular, to a car speed alarm system.
2. Description of Related Art
Due to the popularity of cars, there are more people driving their own cars. A direct consequence is that there are more car accidents. Among all accidents, collisions from behind are the most common type.
One primary cause of collisions from behind is either the distance between cars is too short or the car speed is too fast. If a car in the front suddenly decelerates, the driver of the car directly behind often does not have sufficient time to react, resulting in collisions. To reduce the above-mentioned car accident rate, people often put a set of distance check signs at appropriate places (e.g., “0 m,” “50 m,” “100 m,” and “200 m” signs at 0 m, 50 m, 100 m, and 200 m). Alternatively, several car distance alarm lines are drawn at equal intervals on each lane. These methods help drivers keep appropriate distances from the cars in front of them. This can prevent some of the collisions from behind. However, the car distance check sips or car distance alarm lines are installed or drawn at fixed or specific places. Car drivers cannot check the distances at any time.
To notify the driver of the car behind, each car is provided with several brake lights. When a driver steps on the brake, the brake lights are turned on so that drivers of the cars behind can slow down their speeds appropriately. However, the existing brake lights have only ON and OFF states, without providing any additional information. For example, the brake lights cannot provide the car speed information to the drivers behind. Thus, even if the drivers of the cars behind know that the car in the front is decelerating, the collision may still happen because he does not know about how large the deceleration is.